Concept explainers
(a)
Interpretation:
Whether the statement “a sample of potassium chloride from Chile contains the same percent by mass of potassium as one from Poland” obeys the law of mass conservation, the law of definite composition or the law of multiple proportions is to be determined.
Concept introduction:
The law of mass conservation - Introduced by the famous French chemist Antoine Lavoisier, the law states that there is no change in the total mass of the substances that go into any physical or
The law of definite composition - This law can be defined as; a particular compound maintains an exact universal proportion of elements in its composition, irrespective of the source. The proposal for this law was made by Joseph Proust.
The multiple proportions law - The ratio of the weights of an element with variable mass is small whole numbers when it forms more than one compound by combining with an element with fixed weight.
(a)
Answer to Problem 2.14P
The statement “a sample of potassium chloride from Chile contains the same percent by mass of potassium as one from Poland” obeys the law of definite composition.
Explanation of Solution
The law of definite composition explains that a compound is formed upon the
The molecular formula for
The statement “a sample of potassium chloride from Chile contains the same percent by mass of potassium as one from Poland” obeys the law of definite composition due to the presence of one ion each of potassium and chloride in samples obtained from different sources.
(b)
Interpretation:
Whether the statement “a flashbulb contains magnesium and oxygen before use and magnesium oxide afterward, but its mass does not change”obeys the law of mass conservation, law of definite composition or the law of multiple proportions is to be determined.
Concept introduction:
The law of mass conservation - Introduced by the famous French chemist Antoine Lavoisier, the law states that there is no change in the total mass of the substances that go into any physical or chemical reaction.
The law of definite composition - This law can be defined as; a particular compound maintains an exact universal proportion of elements in its composition, irrespective of the source. The proposal for this law was made by Joseph Proust.
The multiple proportions law - The ratio of the weights of an element with variable mass is small whole numbers when it forms more than one compound by combining with an element with fixed weight.
(b)
Answer to Problem 2.14P
The statement “a flashbulb contains magnesium and oxygen before use and magnesium oxide afterward, but its mass does not change” obeys the law of mass conservation.
Explanation of Solution
The reaction for the formation of a molecule of magnesium oxide is as follows:
The equation shows the presence of two atoms of magnesium on each side of the equation. There are two atoms of oxygen on each side of the equation as well. The total mass of the reactants and products can be calculated as follows:
From the calculations above, the observation can be made that the total mass of the reactant is equal to that of the product.
The statement “a flashbulb contains magnesium and oxygen before use and magnesium oxide afterward, but its mass does not change” obeys the law of mass conservation. The comparisons made by calculating the total mass of reactants and products prove it.
(c)
Interpretation:
Whether the statement “arsenic and oxygen form one compound that is
Concept introduction:
The law of mass conservation - Introduced by the famous French chemist Antoine Lavoisier, the law states that there is no change in the total mass of the substances that go into any physical or chemical reaction.
The law of definite composition - This law can be defined as; a particular compound maintains an exact universal proportion of elements in its composition, irrespective of the source. The proposal for this law was made by Joseph Proust.
The multiple proportions law - The ratio of the weights of an element with variable mass is small whole numbers when it forms more than one compound by combining with an element with fixed weight.
The mass fraction of an element in a compound is defined as the ratio of the sum of the masses of all the atoms of that element to that of the mass of one mole of compound.
Mass percent of an element represents the percentage concentration of that element in a compound. It is equal to the mass fraction expressed as a percentage. The general formula to calculate the mass percent of an element A in a compound is as follows:
(c)
Answer to Problem 2.14P
The statement “arsenic and oxygen form one compound that is
Explanation of Solution
The two compounds arsenic formed by the combination of arsenic and oxygen atoms are
The total mass of
Substitute
The mass of arsenic
Substitute 2 for number of atoms of
The formula to calculate the mass percent of arsenic in
Substitute
The total mass of
Substitute
The formula to calculate the mass percent of arsenic in
Substitute
The number of atoms of arsenic being constant in both the compounds, the arsenic atoms combines with oxygen atoms whose proportions are different in both the compounds.
The total mass of oxygen atoms in compound
The statement “arsenic and oxygen form one compound that is
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Chapter 2 Solutions
Connect 2-Year Access Card for Chemistry: The Molecular Nature of Matter and Change
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